Generally, a magnetic disk drive is held in a case provided with a cooling fan as mentioned in Japanese Patent Laid-open No. 4-49590. Usually, the case is placed in a completely air-conditioned room.
Recent vehicles are equipped with a navigation system and other electronic systems. Those in-vehicle systems exchange information with external systems through a satellite, and mails can be sent out and received at optional places by mobile telephones. Thus, the amount of information with which in-vehicle systems need to deal has progressively been increased. To meet such a trend, an information recording/reproducing device for recording and reproducing information including still pictures, animations and music numbers, particularly, a magnetic disk drive is necessary. A magnetic disk drive enables, for example, a navigation system to achieve quick response and information update. A magnetic disk drive is capable of downloading (storing) a large amount of information through a private telecommunication network using ground waves and satellites or the Internet
Usually, the operating environment of a magnetic disk drive was in a room, and the magnetic disk drive was held in a case provided with a cooling fan. It has been a technical subject relating with the temperature of the environment in which the magnetic disk drive operates to control the temperature of a heat source to limit the upper limit of temperature in the magnetic disk drive to, for example, about 50° C.
The temperature of the interior of a vehicle exceeds, sometimes, several tens degrees Celsius when the vehicle is parked under a burning sun in summer and drops, sometimes, below −20° C. when in the morning in winter. A magnetic disk drive mounted on a vehicle is exposed to such a severe thermal environment. In a low-temperature environment, the rotation of magnetic domains and the displacement of magnetic domain walls in a magnetic disk are difficult and the magnetic disk drive is unable to write information to the magnetic disk. In a high-temperature environment, the rotation of magnetic domains and the displacement of magnetic domain walls in a magnetic disk occur easily. Consequently, written information cannot be held in the magnetic disk; that is, the magnetic disk is unable to keep storing information. An in-vehicle magnetic disk drive is required to operate normally under vibrations.